Apparatus for the comparison of colors



Nov.'26, 1935. H. H. SHELDON 2,022,327

'APPARATUSFOR THE COMPARISON OF COLORS Filed June 28, 1932 3Sheets-Sheet 1 INVENTOR (Ira/J11 S e/aon,

I ORNEY Nov.26, 1935. H SHELDON 2,022,327

APPARATUS FOR THE COMPARISON OF COLORS INVENTOR NOV. 26, 1935. SHELDONAPPARATUS FOR THE COMPARISON OF COLORS Filed June 28, 1952 5Sheets-Sheet a A N m w INVENTOR- Harold ff. Shela 011 Patented Nov. 26,1935 UNITED STATES.

APPARATUS FOR THE COMPARISON OF GOLD Harold Horton Sheldon, Yonkers, N.1., assignor to Sheldon Electric Corporation, New York. N. Y., acorporation of New York Application June 28, 1932, Serial No. 619,728

, I Claims. (Cl. 885-14) This invention relates to means for comparingthe color, shade and similar characteristics of materials, whether in asolid, liquid or gaseous state.

My invention discloses apparatus adapted for the commercialaccomplishment of this purpose and adapted for operation by a personcomparatively unskilled in the art of color measurement.

One object 01 this invention is to use photoelectric cells for thesensitive and rapid commercial comparison of various materials.

Another object of this invention is to allow a comparatively unvaryinglight source and a photo-electric cell of a limited range of sensitivltyto be employed with one another for the measurement of materialsreflecting or transmitting light over a wide range of intensity.

A further object is to allow the convenient and rapid interchange ofvarious samples to becompared with one another, whether in solid, liquidor gaseous form.

Another object of this invention is to provide an apparatus wherebyvarious materials may be readily compared with similar materials of astandard color or shade.

A further purpose is to allow'solid samples to be integrated withrespect to their optical properties by a system for moving themcontinuously while being tested.

A further object is to allow such samples to be I optically interchangedwithone another while this integrating motion is uninterruptedlymaintained.

This invention employs certain of the devices disclosed in co-pendingapplication Ser. No. 548,976 filed July 6th, 1931 which has matured intoUnited States Patent No. 1,971,317 issued August 31, 1934..

The arrangement and operation of this invention will be apparent byreference to the following drawings, where: v

Fig. 1 isa sectional elevation of one side of an apparatus disposedaccording to this invention.

Fig. 2 is a horizontal section of the apparatus partly on the planeindicated at 2-2 of Fig. 1.

Fig. 3 is a front elevation of one portion of the apparatus.

Fig. 4 is a detail of the mechanism for controlling the intensity of thetransmitted light.

Fig. 5 is a detail of the device for rapidly interchanging samples inrotation.

Fig. 6 is a schematic representation of a typical electrical circuitsuitable for one form of the invention herein described. 1

Referring now to Figs. 1, 2 and 3, an outside casing 20 preferably ofheat resisting material is supplied with suitable screen openings 2|,located at the lower portions thereof for the admission or air currentsto carry away the'heat produced therein during operation.

Other screened openings 22 located at the upper portion of the sameserve as outlets for such air current. A bar '23 of suitable mechanicalform serves as a protection for the controls and casters 24 may beprovided in order to allow the convenient movement of the entireapparatus irom spot to spot. A- louvered cover 22 may also be providedto prevent the entrance of unwanted light from the exterior.

. Hinged or removable covers 25 and 26 allow access to the upperportions of the apparatus. A

hinged door 21 allows access to the light generating chamber without thenecessity oi. removing or opening one oi! the larger covers. All thesecovers are preferably made 01 metal or other suitable material, andarranged to close the chambers substantially completely, in an opticalsense.

The light source chamber 28 is separated from the other portions of theapparatus by walls indicated at 29 which are preferably of metal coveredwith heat insulating material such as asbestos, in order to minimizeheat transfer to the other portions of the apparatus. The gen eraldirection of the cooling air currents through the apparatus is indicatedby arrows.

At 30 is indicated the adjusting handle which projects from one side ofthe outer casing and 30 serves to vary the light intensity by actuatingcertain devices within the cabinet, to be described hereinafter.

34 represents a knob extending to one side of the cabinet and allowingthe control of the lateral position of a sliding carrier 35. Carrier 35is provided with suitably grooved openings 36 designed to allow theready insertion and removal of various filters in a convenient solidform such as pieces of colored glass or the like. At 31 is representedanother similar knob which allows control of the position of a secondcarrier 38 also having openings 39 therein. These openings are suitedfor the reception of filters in the form of transparent cells of glass,quartz or the like.

These cells may serve to hold filtering media in the form of liquids orgases.

Carriers 35 and 38 are arranged to slide in suitable supports sothat anyone of the various filter glasses or filter cells carried thereby may beplaced intthe optically active portion of this apparatus.

At 40 is represented an indicating galvanometer optical properties 01'materials to be measured by this apparatus. At 4| is shown a voltmeterwhich 20 stationary frame 48, mounted on one outer wall indicates asimilar adjustable resistance also 7 serving to control an electricalmeasuring circuit.

At 44 is shown a switch readily accessible to the operatoriand servingreadily to changethe sensitivity or measuring range of the apparatusespecially to avoid overloading and/or damaging the indicatinggalvanometer thereof.

Referring now in addition to Fig. 5 the sample holders of this apparatusor the devices adapted to conveniently contain samples of solidmaterials to be compared thereby, take the form of two rotating members48 and 41.

These two members are carried by a normally of an optically enclosedchamber 48. This wall has an opening directly opposite one of the sampleholding members.

The frame and sample holders are adapted to rotate about a commoncentral member 5| by the manipulation of handle 52 and shaft 53associated therewith. A suitable shield 54 may be used to enclose orshield from accidental contact therewith by the operator, the exposedmoving portions of these sample holders. Each sample holder is composedessentially of a rotating member such as48 in the form of a hollow drumhaving a part of its peripheral surface removed in order to allowinsertion of the sample therein and having an optical opening 58 in oneend thereof. This opening is made of uniform size since it determinesthe eifective optical area of the sample tested. A reciprocating piston51 is capable of rotary motion in addition to its reciprocating motionand may be retracted by handles 58 and shafts 58 extending throughsuitable hollow shafts 80. Springs 5| coast with shafts 58 and 88 so asto cause pistons 51 to be normally pressed against the end of drummember 48 which has therein the opening 55.

Rotating members 48 and 41 are arranged with.

suitable bearings and are driven by sprockets 62.

Referring now in addition to Fig. 3, toothed wheels 82 are seen to beprovided with associated sprockets 55 afllxed firmly on the shaft 80 soas to rotate simultaneously therewith. These latter gears 55 are coupledby a chain 58 linking them. Another chain 84 passes over both of gears82 and also over a sprocket 65 upon the shaft 68 of a suitable drivingmotor 81.

An idler gear 88 upon the end of a suitably hinged member 68 is held bymeans of a spring- 58' so as to maintain chain 84 in a suitably tautcondition at all times. Motor 81 may alternatively operate sprocketthrough speed changing gears, if so desired.

When the entire sample holding structure is rotated as a unit aboutshaft 5| by the manipulation of handle 52, chain 54 will remain incontact with at least one of the sprocketwheels 82 at all times, by theaction of idler wheel 88. Likewise at such times as only one ofsprockets 82 isin contact with chain 84, the other sprocket 82 will bemaintained in continuous rotation through the intermediary action ofsprockets 55, chain 83 and shafts 88.

The samples to be measured, when in a suitable solid form, may be placedbetween piston 51 and the open end of drum'48, while piston 51 isretracted by means of handle 88. Spring 8| will then serve to causepiston 51 to hold the sample firmly when handle 58 is released and whilethe sample holder is in rotation.

Other relative sizes and mechanical forms of 5 such holders may be usedto suit the type of samples to be inserted therein, such as cylinders inwhich textiles may be inserted and the like.

When handle 52 is turned, one sample holder will take the place of theother immediately be- 10 fore aperture 88, without interrupting theindividual rotary motion of the samples in the two holders. This allowsthe comparatively rapid interchange of two samples, both of them beingrapidly and continuously rotated. This doubie assembly may manifestlyeasily be altered to allowdthree or more individual sample holders to beuse Describing now the optical system of my invention, Hi indicates asuitable source of light such 29 as a concentrated filament incandescentlamp, mounted in a suitable socket H. The light from this lamp isconcentrated by means of a suitable lens system II which may be insertedin a transverse heat insulating partition 1 I mounted with- 25 in thecover 25 and forming a closure with one of the walls 29 for the chamber28. This lens system may consist of any suitable combination of lensesand/or filters. Such lenses and/or filters may be constructed of heatresisting material, or of material which exerts a filtering action uponheat rays in order to prevent the passage of undesired heat rays throughthe same.

At 13 is indicated another lens held in a suitable framework 14 fastenedto the partition 1!. Lens I8 is arranged to concentrate the light raysupon the surface of the sample which lies immediately behind opening 58.

The light directly reflected from the surface of the sample reaches thewalls of chamber 49, 40 and is absorbed by these walls which may belined with a suitable material for this purpose, such as black paint ofa high light absorption factor, or the like.

The secondary light rays proceeding from the 45 surface of the sampleand due to its illumination by light source in proceed through lenses l5and 16, which may constitute an optical system suited to concentrate anddirect the light. Between these two lenses may be interposed an irisdia- 50 phragm 88, for controlling the light passing therethrough.

Referring now also to Fig. 4, the details of this iris diaphragm and itscontrol are as follows: suitably shaped plates 8| coact with one another55 to change the size of optical aperture 82 when control lever 83 ismoved in an are about the periphery of the diaphragm assembly. Thedetailed construction of such iris diaphragms is well known in thephotographic art and accordingly 60 it is not shown or described indetail.

Actuating member 83 is provided with a slot 84 extending radiallytherein. An arcuate member 85 swinging upon pivot 88 between the limitsindicated by' the full lines and the dotted lines 65 of Fig. 4, servesto move member 83 by means of pin 81 which engages slot 84. A suitableweight 88 may be employed upon one end of member 85 to ensure itsdescent under the influence of gravity when it is not supported. At 89is indicated 70 a shaft which is afflxed to handle 38 and drum 3! so asto rotate therewith. This shaft turns in bearings 98 and 8! and carriesa suitable cam member 92. This cam operates to raise and lower themember 85, which latter actuates the dia- 7 phragm proper. A suitablebearing surface 93 may be provided upon member 85 against which cam 92may bear. I

At a. suitable point along shaft 891s provided a pulley 94. A counterweight 95 hangs by means of a cable or rope 99 whose other extremity isafiixed to pulley 94 in such wise as to tend to rotate the latter in onedirection.

The downward pressure bf member 85 due to the gravitational pull uponthe amxed weight 88, acting upon cam 92 tends to cause shaft 89 torotate in a certain direction. Cable 96 is so disposed upon pulley 94 asto tend to rotate shaft 89 in the opposite direction by the force due togravitational action upon the counter weight 95 suspended from cable 96.This system of weights and counter balances and a friction spring 3I'are designed to secure the effect that drum 9! and iris diaphragm 8|will remain in the position in which they are placed, until moved by themanipulation of handle 39, which latter ac tion will cause the irisdiaphragm to open or close to a degree proportional to the degree ofrotation of the handle and to the form of cam 92, whichform can be madesuch, by well-known methods of computation, that the light admittedthrough the diaphragm will be proportional in a linear or other fashionto-the degree of angular rotation of handle 39, or to any desiredfunction thereof.

The light rays after passing through the optical control systemcomprised by lenses I5 and I6 and the iris diaphragm 99 between them,are now projected through the filter devices and 38 previouslydescribed.

These devices allow any desired material, either in solid, liquid orgaseous form, to be placed so that the projected beam of light must passthrough it. The employment of two such filters, one adapted to holdsolids and the other liquids or gases, allows the operator to employ alarge choice of filters and/or to use two filters at the same time. Thefiltered light rays now enter an opaque light chamber I99. Within thischamber is situated a photo-electric cell I9I placed in a suitablesocket I92. This cell may be of any type well known in thephoto-electric art, such as of the potassium or caesium oxide types. Theelectric current derived from the operation of this cell is transmittedby suitable conductors, preferably short and extremely well insulated,to an amplifying tube I93 located immediately behind and exterior to thetube chamber I99. This tube is also located in a suitable socket I94 andmay be of any type suitable for connection to a photoelectric cell foramplifying purposes.

Referring now to Fig. 6, there is here shown a schematic diagram of aform of electrical circuit serving to interconnect the variouselectrical components of this apparatus, to exercise suitable control ofthese components and to allow the ultimate readings of galvanometer 49to be interpreted in terms of the optical properties of the samplesunder test.

The power supply lines indicated at H9 pass through a suitablecontrol'switch III and then have bridged across them the light source I9with a suitable series controlling resistance II2 which may be manuallycontrolled or of a form operating automatically or semi-automatically soas to keep the voltage impressed upon the lamp '19 substantiallyuniform. A voltmeter 4I is also bridged across the light source so as toindicate to the operator when adjustment of the various voltage controlsmay be-needed. It may sometimes be found desirable to connect this meteracross thepower lines rather than the light source.

These power lines also serve to actuate motoit 61 through the left handblade and contacts of 5 switch II 9, when the latter is in the closedposition. A transformer II4 also has its primary bridged across thesepower lines through a suitable controlling resistance 4' which may beeither of the manually controlled or of the auto- 19 matic type. Thistransformer has its primary wound to a voltage corresponding to that ofthe power supply and its secondary wound to produce a voltage andcurrent suitable to operate the cathode heater N5 of amplifying tubeI93, or the i5 filament of 9. directly heated type of tube which may beused in lieu of the indirectly heated type here shown.

Amplifying tube I93 as herein shown is one having a separately heatedcathode H6, which is 20 connected to the electrical midpoint of heaterII5 by means of a. mid-tap connection Ill extending therefrom to theelectrical center of the secondary winding of transformer I I9.

It is understood that a directly heated cathode 25 may be employed, inwhich case no external connections of cathode and heater will be neededsince they will then be physically identical. This point of connectionis taken as the point of minimum potential of the'circuit and is con- 99nected to a suitable intermediate point .I I8 of a high voltage supplybattery II9, chosen as hereinafter described.

The operation of the circuit now to be described is that havingreference especially to the 35 currents derived from the action ofphoto-electric cell IIII. When switch H3 is closed the right hand bladeand contacts thereof close the circuit to indicating galvanometer 49.This control connection is so arranged in order that galvanometer 40 49may be connected to the circuit only when motor 61 is also connected,and also in order to avoid any overload or excessive currents throughthe galvanometer. The output from the high potential terminal I29 ofbattery .I I9 passes through conductor I26 'to a suitable regulatingresistance I2! and then branches through two arms of a bridge structure.In one arm of this structure is found fixed resistance I 2|, variableresistance 42 and battery control switch I 22, which latter 50 serves toprevent current from battery II9 flowing through this arm of the bridgewhen such current is not needed for measuring purposes.

If battery I I9 be replaced by a substitute source of potential,actuated from power supply lines I I 9 through switch I I I, switch I22may be omitted, as switch III will then also control such substitutepotential supply.

This arm of the bridge also contains variable resistance 43 which servesto control the total value'of resistance in this arm. The other arm ofthe bridge contains another fixed resistance I23 similar in value toresistance I2I, and another variable resistance 42 which may beidentical with that in the first described arm. In this arm of thebridge is also located the internal or space impedance of tube I93,existing between its anode I24 and its cathode H6. The return from thecathode IIB is made through conductor I25 extending from the point ofminimum potential of the circuit back to a suitable point upon powerbattery I I9 as hereinbefore described.

' Photo-electric cell I9I' is bridged between conductor I28, whichconnects resistance I2I to high potential point I29, and the controlgrid I21 of I21 and cathode I I6 is interposed a suitable conductivebiasing circuit comprising coupling resistance I28 and the portion I29of battery H0 which thus serves to bias this control grid to a suitablenegative potential.

It is to be understood that all the electrical components of thiscircuit have been illustrated by conventional devices such as batteriesand transformers which by appropriate artiflces may be substituted forone another according to principles well known in the electrical art.

It is also to be understood that other power supplies such as so-calledB eliminators or continuous current generators may be substituted forbattery I I9 or any of the divisional parts thereof. While not confinedto any particular values of potentials or resistance, which may ofnecessity vary with the electrical constants of the photoelectric cells,batteries, transformers, amplifying tubes and the like employed, it hasbeen found that the following values are suitable with come mercialapparatus now available. Amplifying tube I03 may have a heater circuitemploying a potential of 2.5 which latter will accordingly be thesecondary potential of transformer I I4. The primary voltage of thistransformer and that of power mains H0 may be 110 volts A. C. In casethat the power supply is D. C. other suitable electrical apparatus forvoltage reduction should be substituted for transformer I I4 as wellknown in the art. Light source I0 and its resistance II2 should be soproportioned that the total voltage drop across the two will beapproximately that of power supply through mains IIO. Motor 61 as hereindicated has an A. C. motor, but if the power supply through mains I I0is D. 0. this motor must be of a corresponding type.

The galvanometer may have a suitable protective series resistance I30 of750 ohms and a, suitable potentiometer type shunt resistance I3I of 1000ohms, switch 44 serving to utilize one or both of these r:sistances asoccasion demands.

Battery II9 may have its high potential lead I20 furnishing a positivepotential from volts upwards and its low potential lead I29 furnishing anegative potential of 9 volts to the control grid of tube I03. The gridresistor I28 may be of the order of 10 megohms. Resistances I2I' and I23may be 50,000 ohms each and resistances 42, 18,000 ohms each. Thesensitivity resistors I2I and I32 may be variable from 200,000 ohmsdownwards.

Resistor 43 should be preferably of a value commensurate with the outputimpedance of tube I03, which for the type shown may be of an order ofmagnitude between 5000 and 15,000 ohms, but may be greatly below or inexcess of these values for other types of amplifying tubes.

The adjustment of the electrical circuit above described will be evidentto one skilled in the art, as it comprises the adjustment of a bridgecircuit having photoelectric cell I0! in one arm thereof, and theadjustment of the variable resistors until a null indication is securedat galvanometer 40.

When light impinges upon cell IOI, the bridge will be thrown out ofbalance by the changing of the anode resistance of tube I08 due tovariations in the potential impressed upon its control grid I21 throughthe current recrived from photo-electric cell IOI Galvanometer 40 willaccordingly show a deflection which may serve as a measure of the lightfalling upon cell It.

For great ranges of light values it may be amplifying tube I03. Betweenthis control grid preferable to alter the resistances controllinggalvanometer 40 and use such alterations which may be necessary torestore galvanometer 40 to the null point as indications of the degreeof illumination reaching cell IN. 5

In addition to the electrical controls just described it is alsopossible with this apparatus to employ the indicating marks upon theperiphery of the drum 3| which coincide with the fixed contacting pin33, as a measure of the light 10 intensity reaching diaphragm 80. Inthis case the degree of closure of this diaphragm which is necessaryinorder to give identical or proportional readings upon galvanometer 40when different samples are compared can serve as a 5 measure of therelative light intensities when different strengths of light impingeupon this diaphragm.

While I am not limited to any particular method of working the apparatusof my inven- 0 tion, one method which may be employed is to place thesamples to be compared with one another in the sample holders and toexpose them alternately to the light rays from lamp 10 by appropriatemanipulation of handle 52, noting 25 the respective readings, ofresistances 42 or of diaphragm indicating drum 3| as above described,

or noting the deflections of galvanometer 40.

In the case of certain materials such as plush or the like, it may befound advisable to arrange 30 the sample holders of my invention so thatthey will wobble about their axes. This insures the light penetrating inall directions as far as possible into the surface of such types offabrics and avoids inaccurate readings when such ma- 35 terials arebeing tested. For a similar purpose the sample holder itself may besimultaneously vibrated or rotated about an axis which is not concentricwith its own primary axis of rotation.

Alternative methods of integrating the light re- 40 flected from samplesmay be used. For example the photoelectric cell alone or together withits associated optical system may be rotated so as to receive lightreflected at different angles from the sample surfaces. Likewise thelight source 45 may be rotated in similar fashion, or rotating mirrorsmay be used to reflect the light impinging upon the samples or reflectedtherefrom, so as to produce or utilize various angles of reflection.

The use of color filters of this invention is well 50 known and isaccordingly not described in detail. Such filters allow the light to beanalyzed and tested for various components thereof. In case thattheactual samples being tested are liquid or gaseous in nature, they maybe placed 55 in one or more of the cells which ordinarily are utilizedto hold liquid or gaseous colored filters. In this last case standardreflecting blocks of a suitable material such as magnesium carbonate orthe like may be placed in one of the rotating 60 sample holders, whichthen will serve as a secondary source of illumination.

While there have been indicated certain mechanical arrangements of theparts of this invention, it is not confined to such exact arrange- 65ments, but other corresponding or equivalent arrangements which givesimilar results may be employed in lieu of those shown. Accordingly thisinvention is limited only by the scope of the hereunto appended claims.7

I claim:

1. In electro-optical comparison instruments acting upon a plurality ofsamples to be compared, means for rotating said samples substantiallysimultaneously, means for exposing to a 7 stantially horizontaldirection, light controlling and light translating means in the path ofsaid reflected beam, suitable indicating means connected tosaid lighttranslating means, and means for rapidly substituting the sample holdersfor one another in the path of the light beam while uninterruptedlymaintaining said holders in rotation.

3. An optical comparator including means for producing light, means fordirecting it upon a single sample, supporting means for a plurality ofsamples including a rotatably mounted carrier,

a plurality of spring-pressed clamping members,

a tubular support rotatably mounted on said carrier for each clampingmember, said clamping members and said supports forming part of saidcarrier and rotating therewith, means for simultaneously rotating bothof said tubular supports,

means for rotating said carrier so that only one sample at a time isexposed to said light, and

electro-optical means measuring the optical re action of the sample uponwhich the light is directed.

4. Color comparing apparatus including means for illuminating a singlesample, sample changdriving motor having a shaft, a sprocket aflixed 5to said motor shaft and rotated thereby, a driving'mechanical linkthreaded over all of said sprockets, an idler sprocket also threaded bysaid link, means for maintaining said idler sprocket under tension,means for rapidly interchangeably positioning either of said sampleholders in the light from said illuminating means and for rapidlyinterchangeably positioning their respective shafts and sprockets whilemaintaining said mechanical link operatively threaded over all of saidsprockets and electro-optical means measuring said illuminated sample.

5. Optical testing apparatus including means for illuminating at any oneinstant a single sample, means for rapidly interchangeably positioning aplurality of rotating sample holders in the light from said illuminatingmeans, said positioning means including a central shaft rotatable insuitable bearings, a plurality of auxiliary shafts substantiallysymmetrically grouped about said central shaft and rotatable in bearingsafiixed to said central shaft, a plurality of sample holders mountedrespectively on said auxiliary shafts, sprockets aflixed to saidauxiliary shafts and actuated by a chain drive passing thereover, otherauxiliary sprockets affixed to each of said auxiliary shafts andconnected together by an auxiliary chain drive passing thereover, andelectro-optical means measuring said illuminated sample.

HAROLD HORTON SHELDON.

